Conventionally, the weft thread blowing nozzles are arranged to pivot or tilt with the reed of the loom. It is also conventional to arrange a funnel shaped alignment device between the nozzles and the entrance to a weft thread guide channel formed by the teeth of the reed. Such a conventional alignment device has an inlet funnel opening corresponding to the full diameter of the nozzle bundle and an outlet diameter corresponding substantially to the reduced cross-sectional width of the alignment device.
This type of alignment device has certain drawbacks, especially where for multi-color weaving an individual weft thread insertion nozzle is provided for each thread having a different color. These insertion nozzles are collected into a bundle and the blow fluid mixing pipes of the individual nozzles are arranged with equal spacing from the loom shed.
Pneumatic looms are also equipped with means for forming weft thread guide channels. For this purpose it is, for example, conventional to equip the reed of the loom with reed teeth having profiled projections for forming the guide channel. These projection confine the guide channel from above and from below leaving one side of the channel open for the beat-up of the weft thread. The available cross-sectional area of so formed guide channels is relatively small and this is desirable for assuring a proper guiding of the weft thread as it is being inserted and also for keeping the quantity of blowing medium for the weft thread insertion as small as possible. It is also desirable that the weft thread is always travelling through the guide channel along the same path which additionally shall be the most advantageous path. In looms weaving multi-colored fabrics a plurality of weft thread insertion nozzles are arranged in a bundle for the insertion of threads having different colors. It is this type of arrangement of the blow nozzles which prevent satisfying without difficulties the double requirement that the travel path through the guide channel shall always be the optimal path and always the same path for all threads. Thus, attempts have been made to arrange the nozzles in a displaceable manner or to arrange them in a revolving manner so that it would be possible to bring the nozzle of the selected weft thread into the most advantageous position from which the nozzle previously occupying that position had to be removed. This solution to the above mentioned problem requires a complicated and hence costly construction. Due to its complicated movable components the construction is sensitive to external influences and it is trouble-prone.
Even if only a few individual nozzles are assembled into a compact bundle, the available cross-sectional area of the guide channel is frequently insufficient in order to be able to mount the nozzle bundle in a fixed location. This is so because the fluid flows from the individual nozzles travel through the guide channel along flow paths which differ from one another and, at least partially are not following the most advantageous path through the guide channel. Frequently, the thread end impacts on the edges of the reed teeth which define the guide channel. As a result, a substantial proportion of the kinetic energy exerted by the fluid flow is lost so that the thread insertion speed is impaired and the insertion time is lengthened. Further, it is quite possible in conventional devices that the thread being inserted is snarled or jammed up with all the disadvantageous consequences, for example, the formation of undesired loops. Thus, it is not possible to achieve an optimal weft thread insertion where a plurality of weft thread inserting nozzles are arranged in fixed positions because from these positions it is not possible to cause each weft thread to follow the most advantageous path through the guide channel.
To avoid the above problems European Patent Publication 184,435 discloses an arrangement in which the mutual location of the blowing nozzles in the bundle relative to each other is fixed and wherein the flow direction or movement direction of the fluid flow out of each nozzle is individually influenced for directing the respective weft thread advantageously into the guide channel. The just mentioned European Patent Publication 184,435 discloses a weft thread insertion mechanism for looms capable of weaving multi-colored fabrics. The bundle of nozzles is provided with a centrally located fluid flow guide body having an elongated shape with a diameter that first increases in the flow direction and then again decreases. A fluid flow coming out of one of the nozzles follows the shape or contour of the fluid flow guide body so that the weft thread is accordingly deflected, thereby bringing the weft thread approximately into a path through the center of the nozzle bundle. This type of arrangement intends to make sure that a weft thread to be inserted will always take up the same position or rather follow the same path within the guide channel independently of the particular nozzle which inserted the thread. As a result, the cross-section of the guide channel can remain relatively narrow. However, it is a disadvantage of this type of arrangement that the degree of fluid flow deflection depends on the flow speed and thus on the pressure of the available flow medium. Further, the flow guide body must be relatively large while the obtainable effect is not so strong that the required deflection angles for the weft threads are achieved when the nozzle bundle is large as is the case where threads of different colors are to be inserted for the weaving of the multi-colored fabrics. The particular shape of the central flow guide body has a great influence on the weft thread insertion with the added disadvantage that the influence depends on the type of thread involved. Threads with a smooth surface are, for example, influenced in a different way than threads with a rough or coarse surface.
German Patent Publication (DE-OS) 3,415,052 describes another device in which several blowing nozzles are collected into a bundle and a special mechanism is provided for the clean weft thread insertion into the guide channel in the reed. The bundle of blowing nozzles is secured to the loom sley so that the nozzle bundle pivots with the loom sley. However, the individual position of the nozzles relative to each other within the bundle remains unchanged. the guide channel is formed by upper and lower rows of projections of the reed teeth forming the reed. The special mechanism referred to as alignment aid is arranged between the guide channel of the reed and the blowing nozzles. This mechanism comprises a body having a funnel-shaped bore with a funnel-shaped opening facing the blowing nozzles and an exit opening facing the guide channel. The diameter of the funnel opening corresponds at least to the total diameter of the blow nozzle bundle. The diameter of the exit opening corresponds approximately to the cross-sectional width of the U-shaped guide channels through the reed. The blow nozzles, or rather the bundle of blow nozzles and the alignment aid are secured to the reed beam so that they tilt or pivot together with the weaving reed. The alignment aid makes sure that the weft thread entry into the guide channel is centered for all blowing nozzles of the bundle. After the weft thread has been inserted, it is cut at the moment of the reed beat-up. The cutting takes place either between the reed and the alignment aid or between the blow nozzles and the alignment aid. Thus, at least on one side of the alignment aid a certain spacing is required between the alignment aid and the neighboring component, namely the nozzles or the reed in order to provide room for the weft thread cutting element such as a scissors and possibly also for a weft thread clamp. The disadvantage of this conventional arrangement is seen in that the weft thread waste is substantial due to the required location of the weft thread cutting scissors.
The above mentioned German Patent Publication (DE-OS) 3,415,052 also discloses that the bundle of blow nozzles can be mounted in a fixed position and only the alignment aid is mounted to the reed for tilting with the reed. In such an arrangement the weft thread insertion can take place only when the blowing nozzle, the funnel-shaped alignment aid, and the reed channel are arranged in alignment with one another. This situation is present only for a very short time and that available time may be too short for the proper weft thread insertion.